Abstract In situ, three-dimensional (3D) characterizations of particle breakage in porous carbonate sands are presented, for the first time, with synchrotron-based micro computed tomography. Evolution of grain-scale characteristics are identified and quantified via elaborate image processing and topology analyses. The sequential 3D images reveal distinctly different fracture mechanisms for carbonate sands from silica sands. The angular shape of carbonate sand particles facilitates bending fracture, and particles with a lower sphericity and a higher porosity are more prone to break. 3D crack networks extracted from fractured particles imply considerable cleavage along initial pores. The fractal dimension of crack networks increases with external loading due to crack branching via cleavage. The resultant fragment size distribution also appears fractal and the fractal feature is valid down to the breakage limit of calcium carbonate. Crack propagation along the initial pores reduces the energy barrier for particle breakage and thus fracture strength of particles.

中文翻译：

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多孔碳酸盐砂颗粒的分形破碎：微观结构和机制

摘要 首次使用基于同步加速器的微型计算机断层扫描技术对多孔碳酸盐砂岩中的颗粒破碎进行了原位三维 (3D) 表征。通过精细的图像处理和拓扑分析来识别和量化颗粒尺度特征的演变。连续 3D 图像揭示了碳酸盐砂与硅砂明显不同的断裂机制。碳酸盐砂颗粒的棱角形状有利于弯曲断裂，球形度低、孔隙率高的颗粒更容易破碎。从断裂颗粒中提取的 3D 裂纹网络意味着沿初始孔隙有相当大的解理。由于通过解理产生裂纹分支，裂纹网络的分形维数随着外部载荷的增加而增加。由此产生的碎片大小分布也出现分形，分形特征在碳酸钙的破碎极限下都是有效的。裂纹沿着初始孔隙的传播降低了粒子破裂的能量势垒，从而降低了粒子的断裂强度。